Maternal Obesity and the Risk of Infant Death in the United States
Aimin Chen,a Shingairai A. Feresu,b Cristina Fernandez,c and Walter J. Rogand
Background: Maternal obesity (deﬁned as prepregnancy body mass index BMI 30 kg/m2) is associated with increased risk of neonatal death. Its association with infant death, postneonatal death, and cause-speciﬁc infant death is lesswell-characterized. Methods: We studied the association between maternal obesity and the risk of infant death by using 1988 US National Maternal and Infant Health Survey data. A case-control analysis of 4265 infant deaths and 7293 controls was conducted using SUDAAN software. Self-reported prepregnancy BMI and weight gain were used in the primary analysis, whereas weight variables in medical recordswere used in a subset of 4308 women. Results: Compared with normal weight women (prepregnancy BMI 18.5–24.9 kg/m2) who gained 0.30 to 0.44 kg/wk during pregnancy, obese women had increased risk of neonatal death and overall infant death. For obese women who had weight gain during pregnancy of 0.15, 0.15 to 0.29, 0.30 to 0.44, and 0.45 kg/wk, the adjusted odds ratios of infant death were 1.75 (95%conﬁdence interval 1.28 –2.39), 1.42 (1.07–1.89), 1.59 (1.00 –2.51), and 2.87 (1.98 – 4.16), respectively. Nonobese women with very low weight gain during pregnancy also had a higher risk of infant death. The subset with weight information from medical records had similar results for recorded prepregnancy BMI and weight gain. Maternal obesity was associated with neonatal death from pregnancycomplications or disorders relating to short gestation and unspeciﬁed low birth weight. Conclusions: Maternal obesity is associated with increased overall risk of infant death, mainly neonatal death. (Epidemiology 2009;20: 74 – 81)
aternal obesity (often deﬁned as prepregnancy body mass index BMI 30 kg/m2) increases the risk of 1–7 fetal death. Several studies have suggested that maternal obesityincreases the risk of neonatal death, deﬁned as death in the ﬁrst 7 or 28 days of life.1,2,5,8 –10 Previous studies have also suggested adverse effects of maternal obesity on the overall risk of infant death.11,12 Lucas et al11 reported increased risk of mortality up to 18 months in preterm babies born to obese mothers, but the study was limited to babies with birth weights of 1850 g. Baeten etal12 found the risk of infant death doubled in obese women compared with lean women (BMI 20 kg/m2), but the study was limited to nulliparous women, and no distinction was made between neonatal and postneonatal death. No study has examined the effect of maternal obesity on neonatal and postneonatal death separately. There is also a lack of research into the causes of infant death associated withmaternal obesity.5,11 Moreover, most studies of maternal obesity and neonatal or infant death have not taken into account weight gain during pregnancy,5,8 –11 which may modify the risk associated with maternal obesity. To address these questions, we analyzed data from the 1988 National Maternal and Infant Health Survey (NMIHS) to investigate the effect of maternal obesity on infant death. Although thedata were relatively old, NMIHS is the most recent national dataset for this analysis. Few states have added maternal prepregnancy weight and height to the birth certiﬁcate, as recommended in the 2003 model birth certiﬁcate.13 We quantiﬁed the risk of infant death, neonatal and postneonatal death, and cause-speciﬁc death by using this nationally representative dataset.
Submitted 20December 2007; accepted 21 July 2008; posted 23 September 2008. From the aDepartment of Preventive Medicine and Public Health, Creighton University School of Medicine, bDepartment of Epidemiology, College of Public Health, University of Nebraska Medical Center, Omaha, NE. c Department of Pediatrics, Creighton University School of Medicine, Omaha, NE; and dEpidemiology Branch, National Institute of...